I took ~1000 mg of DXM once, and definitely regret it to this day.  It was the time that I finally 'woke up' and I still think I'm working through it over a year later, not helped by past entheogen use.  The biggest advice would be figuring out what in your life drives you to use to such extremes and correct it.  If uncorrectable, learn another less self-destructive activity to engage in.